A linearly operating side-locked padlock of U.S. Pat. No. 4,742,700 was disclosed by the same applicant of this application, in which the dials 3 are rotated to their opening numbers as predetermined to drive the clutch wheels 4 to their opening position, and the button 221 is depressed downwardly to lower the movable shackle fastener 23 to unlock the upper shackle 21 so that the opening or closing of the shackle is linearly operated by a user's single hand. It is really quick to operate the lock. However, when depressing the button 221 for opening the lock, one user's hand should hold the rectangular casing 1 to allow his (her) thumb to depress the button 221 and his (her) other fingers may not firmly clasp the movable shackle 23 to allow an opening stroke of the movable shackle 23, resulting in an unstable holding of the padlock. The opening movement of the movable shackle 23 may possibly injure the user's fingers as jammed between the shielding plate 232 and the right side wall 103 of the casing 1. So, the applicant's prior invention of U.S. Pat. No. 4,742,700 still has some drawbacks on an ergonomics point of view. It is therefore expected to invent a combination padlock to overcome the aforesaid ergonomic drawbacks.